Wonder Boy begins as per the original game—a blonde haired boy wearing a loincloth. Very soon, however, he is equipped with a sword, which is his primary weapon for defeating the opponents that he will encounter. As with the first game, the aim is to get from point A to point B. Unlike the first game, the levels no longer run strictly from left to right—it is possible to move everywhere on the map, and some levels can be rather labyrinthine.
Also new to the game is a trading system. Money is obtained by killing enemies or jumping in specific locations to free coins. This money can be spent to obtain boots (which permit Wonder Boy to run swifter and jump higher), armor (protecting Wonder Boy from various degrees of damage), a shield (which can be used to deflect some projectiles fired by opponents), as well as magic spells and healing potions. There are also inns where the player can obtain useful information for a fee, as well as a drink to replenish a small amount of energy.
The exit to most levels are only accessible by means of a key which is obtained by defeating a boss character somewhere in the level.
Wonder Boy in Monster Land is by far the most difficult title in the Wonder Boy series because there is no continue system nor is there a password system available for the console games. For the arcade version, there is no continue system on the final level. The presence of an on-screen hourglass timer limiting the number of minutes a player can stay in a level also adds to the difficulty of the game.
The Master System version contained fewer variations on the music than in the arcade version, and the ZX Spectrum conversion had no music. Most of the conversions were otherwise identical in terms of content to the arcade original, with graphics adjusted to allow for each of the systems' respective capabilities. A notable difference in the Master System version was the addition of an optional boss called "Mr. Wizard."
The PC Engine saw a conversion of the game in the form of Bikkuriman World, with changes made to the characters to conform to what was then a popular anime series. This version was handled by Hudson Soft, which also did conversions of other Wonder Boy games for the console.
Tec Toy, Sega's distributor in Brazil used the Monster World license and code to produce Mônica No Castelo Do Dragão for the Sega Master System. The game was identical in every way to the source material, but characters were replaced with known figures from the Brazilian comics Turma da Mônica (Monica's Gang). Of course, the game was correspondingly translated into Portuguese for the Brazilian market.
An unlicensed version (by Westone) of Monster World was also produced for the Famicom, under the title of Saiyuki World with Sun Wukong of the Journey to the West tale as the central character. This conversion was produced by Jaleco, and although it was never officially admitted that the game was a port of Monster World, the game's levels and gameplay were one-for-one identical. This game would later have a sequel, known in America as Whomp 'Em.